The present invention is directed to a fuel delivery pipe which is used in an electronic fuel injection type automotive engine and which includes an absorb wall surface formed on a wall. A purpose of the fuel delivery pipe is to reduce vibration and noise due to a fuel pressure pulsation induced by a fuel injection.
Conventionally, a fuel delivery pipe for feeding fuel such as gasoline or the like to a plural cylinders of an engine by means of a plural injection nozzles. In this type of fuel delivery pipe, fuel introduced from a fuel tank through an underfloor pipe arrangement is sequentially injected from the plural injection nozzles into a plural air intake pipes or cylinders to mix the fuel with air and thus mixed air-fuel mixture is burned to generate an output of the engine.
This fuel delivery pipe to be often used includes a return type having a circuit to return an excessive fuel to the fuel tank by using a pressure regulator and a returnless type without the circuit to return the excessive fuel to the fuel tank, when the excessive fuel is fed from the fuel tank. Recently, the returnless type fuel delivery pipe is more employed for the purposes of reducing a cost and avoiding a temperature rise of the gasoline in the fuel tank and the like.
In this returnless type fuel delivery pipe, since there is no pipe arrangement for returning the excessive fuel to the fuel tank, when the fuel injection from the injection nozzles to the air intake pipes or cylinders depressurizes an interior pressure of the fuel delivery pipe, this sudden depressurizing and a stop of the fuel injection causes a pressure wave that is transferred to the fuel tank from the fuel delivery pipe and a connection pipe connected to the fuel delivery pipe to be inverted such that the pressure wave is returned from a pressure controlling valve within the fuel tank to be transferred to the fuel delivery pipe through the connection pipe. The fuel delivery pipe is provided with the plural injection nozzles for injecting fuel sequentially, which causes the pressure pulsation. As such, the pressure pulsation is transferred to an interior of a car through clips for securing the underfloor pipe arrangement. This noise brings a discomfort to a driver and fellow passengers.
To suppress a problem due to the pressure pulsation as stated above, conventionally employed as disclosed in Japanese Patent Laying-Open No. 2000-329030 is such a method that the fuel delivery pipe is formed with a flexible absorb wall surface on a wall surface for absorbing and reducing the fuel pressure pulsation induced by the fuel injection such that the absorb surface is flexed and deformed by receiving a pressure caused by the fuel injection. With such a method, low-frequency component equal to or less than several tens of Hz of the fuel pressure pulsation can be suppressed.
However, a formation of the flexible absorb wall surface on the wall surface of the fuel delivery pipe as stated above allows a standing wave caused within a body of the fuel delivery pipe transfers from a high-frequency area to a low-frequency area, resulting in that the standing wave transfering to the low-frequency area causes new vibration and noise. Specifically, as shown in Japanese Patent Laying-Open No. 08-193553 and FIG. 30, fuel introduction pipe 52 is conventionally securely connected to one end of fuel delivery pipe body 51 to arrange opening 53 of fuel introduction pipe 52 at one end of an interior of fuel delivery pipe body 51. Therefore, as shown in FIG. 31, opening 53 of fuel introduction pipe 52 is arranged in the vicinity of an antinode where the standing wave caused within fuel delivery pipe body 51 becomes to be a maximum amplitude, thereby raising a problem that the pulsation transfer becomes large due to a first mode of the standing wave as illustrated by a solid line in FIG. 31 and a second mode of the standing wave as illustrated by a dashed line also in FIG. 31.
To resolve the above problem, such a method as shown in Japanese Patent Laying-Open No. 2000-329030 and FIG. 32 is known to public that fuel introduction pipe 52 is arranged to be connected with fuel delivery pipe body 51 vertically in order to arrange opening 53 of fuel introduction pipe 52 in the vicinity of a center within fuel delivery pipe body 51. With such a method, fuel delivery pipe body 51 and fuel introduction pipe 52 are connected to each other in such a manner as shown in FIG. 33 that opening 53 of fuel introduction pipe 52 is arranged in the vicinity of a node of the first mode of the standing wave to suppress the transfer of the first mode of the standing wave, thereby being capable of suppressing vibration and noise of a car.
However, if fuel introduction pipe 52 is connected to fuel delivery pipe body 51 vertically in such a manner as disclosed in Japanese Patent Laying-Open No. 2000-329030 and FIG. 32, there arise problems such as an interference with other automotive parts and shortage of clearances, resulting in a drawback of an awful layout.
To resolve such problems, there are disclosed the fuel delivery pipes which can resolve the problems of the interference with other automotive parts and shortage of clearances and achieve a good layout, respectively, by FIG. 4 of Japanese Patent Laying-Open No. 2000-329030 in which the fuel introduction pipe is inserted from one end of the fuel delivery pipe in a longitudinal direction to arrange the opening of the fuel introduction pipe in the vicinity of a center of the fuel delivery pipe and by Japanese Patent Laying-Open No. 2000-329031 in which the opening of the fuel introduction pipe is inserted vertically to the fuel delivery pipe to be arranged therein and the fuel introduction pipe is designed into L-shape to arrange the underfloor fuel introduction pipe arrangement in parallel with the fuel delivery pipe.
However, since the opening of the fuel introduction pipe according to each of FIG. 4 of Japanese Patent Laying-Open No. 2000-329030 and Japanese Patent Laying-Open No. 2000-329031 is positioned in the vicinity of the node of the first mode of the standing wave, it is possible to suppress the transfer of the fist mode of the standing wave as stated above, whereas since the opening of the fuel introduction pipe, at the same time, is positioned in the vicinity of the antinode of the second mode of the standing wave, the pulsation transfer of the second mode of the standing wave becomes large to have raised problems of vibration and noise at around 1 kHz induced by the second mode of the standing wave. Alike what is disclosed in Japanese Patent Laying-Open No. 2000-329031, if the fuel introduction pipe is bent into L-shape in order to improve a placement layout, a L-shaped joint is required for connecting with the fuel introduction pipe, resulting in a drawback of increasing a manufacturing cost.